(a) Field of the Invention
The present invention relates to a protection device and a method that detect electricity, and more particularly to a protection device and a method that are applied to a power extension cord and are assembled on extension sockets to provide a notification of power consumption for loaded electric appliances, so as to enable a user to trade off power usage and to prevent from an unexpected incident in advance, as well as to automatically give off a warning signal or shut down the power when the power extension cord is overloaded, thereby acquiring a function of safety maintenance, self limiting time of use, and assuring a safe usage.
(b) Description of the Prior Art
It is known that in using an electric product, a user will insert a power plug of the electric product into a power outlet on a wall. If the electric product is still at a certain distance from the power outlet on the wall, then a power extension cord will be used for adaptation, such that the electric product can be used at any place.
All of the existing power extension cords are provided with marks of safety regulations. When the power extension cord is plugged with too many electric products and once the power load is exceeded, the power extension cord will automatically shut down the power to avoid danger. Although the power extension cord is provided with a specification of power safety regulations, the user will usually ignore the safety regulations written on the power extension cord while using the power extension cord, and plug multiple electric products on the same power extension cord for use, which will easily result in danger. In spite of the aforementioned protection device, it is still easy to cause danger under a condition of unstable power source. In addition, as the power extension cord is used for a long time, its wiring material will have a change of physical property, such as an increase of impedance of a lead wire, or a decomposition and embrittlement of an insulator. In this case, time of its availability should be estimated and when that time is reached, the power extension cord should be discarded to maintain safety.
The most efficient method for maintaining safety of the power extension cord is to keep the total load explicitly below a practical value specified by the safety regulations. This operation is dependent upon the user's decision; for example, it is preferred to keep the total power consumption below 80% of the regulation. However, as the conventional design is not able to allow the user to acquire related data at any time, it is unable to carry out a preventive operation in advance.
All of the conventional safety devices are designed to operate when the load is exceeded or a critical load value is achieved, and the user can not access information of electricity in a range between the lowest load and the highest critical load value at any time. For example, a safety limit of an extension cord to be used is set to 600 W, and its work load of use has achieved 595 W (ignoring an allowable error). If power is unstable or one of its electric products is short-circuited, then the extension cord will be substantially overloaded, forming a significant creepage or trip sparks, or event resulting in a blowout and burning. In the mean time, other electric products that are in use, such as a computer or any related electric equipment for accessing information, will be affected and shut down, or their logic operation units or programs will be damaged.
Many conventional protection devices are only designed to serve as the protection at an end of incident. For example, an outlet installed on a wall, or a socket of an extension cord, uses temperature or current detection as a reference of protection and only issues a notification signal before a critical load is achieved.
On the other hand, as there are multiple sets of power socket terminal, one to a full number of plugs of electric products can be inserted. However, for the conventional power socket, the power consumption requirement of a single electric product cannot be acquired at any time and at will; for example, the ordinary user is not able to know the power consumption of an electric heater which consumes a large amount of power and overly turns it on at will, because its labeling texts of shipment are tiny, stained, or lost, thereby causing an unnecessary power waste. In particular, under a current situation of energy shortage, if the user can be easily aware of the power consumption, he or she will be able to manually determine the condition of use in accordance with a common knowledge that one kw/h is equal to one degree of power, so as to save the power of use, which will play an important role in reducing the unnecessary loss of global energy.